Although the study of somatosensory systems has elucidated fundamental principles in cortical function, our understanding of the functional operation of these systems under "real world" conditions is limited. In the rat vibrissa (whisker) system, an excellent model in which to explore this issue, previous physiological investigations have been largely limited to single-pulse and periodic stimulation, even though during object exploration a rat will typically experience complicated temporal patterns of vibrissa stimulation. I propose to examine the perception of more realistic stimuli along an axis of stimulus "complexity". Specifically, I will extend previous psychophysical studies by testing the ability of rats to discriminate gratings, which differ in periodicity (the regularity of groove spacings) but not average spatial frequency. I will further quantify, in awake, sedated rats, the cortical neural responses to aperiodic and periodic stimuli, in the context of hypothetical neural codes. Ultimately, a more thorough understanding of neural processing of natural tactile stimuli could guide corrective procedures for impaired tactile sensation and aid the design of more effective prosthesis.